It’s more efficient, but only barely, and most of that power efficiency probably comes from an expected rise to 204-240V mains rather than 120V. Considering their power efficiency is 93% for their calculations, it’s definitely meant for data center usage at higher voltages.

Aside from that, it increases the chip density on the boards, so you get more hashing out of the same real estate, but the chips themselves are the same as the S5, so unless you’re already planning on buying some S5’s for datacenter hosting, it’s not worth it.

On the other hand, if you are planning data-center hosting, it’s a good time to compare prices between S5 and S5+ to determine which one you want on your racks.